Polymeric film structures and packages made therefrom are useful in the packaging field for the packaging of food products, especially respiring food products such as natural cheeses. These film structures and the packages made therefrom generally contain multiple layers of polymers in which each layer adds certain physical or chemical properties to the completed film or package made therefrom.
Certain packaging problems are encountered when packaging respiring food products such as natural cheese (i.e., swiss-type cheese). These packaging problems exist due to the process by which the respiring product is made and the packaging requirements of the final product. For example, swiss-type cheeses are made utilizing specific molds or bacteria to produce the “eyes”, i.e., voids in the cheese that are characteristic of this type of cheese. Specifically, swiss-type cheeses are ripened by typically adding bacteria such as Propionibacter Shermanii to form the “eyes” of the cheese. These “eyes” are formed as gas pockets of CO2 which is given off by the swiss-type cheese. This CO2 elimination not only occurs during production of cheese but continuing during the “life” of the product, including the life of the packaged product. Too much CO2 inside the package causes the package to “pillow.” “Pillowed” packages are negatively received by the consumer. Also, natural food products such as swiss-type cheeses are affected by atmospheric oxygen (O2) during the transporting and storing of this type of product in a package. If the permeability of O2 into a package is too rapid, the product “life” is shorter. Shorter product life affects the financial aspects of the product. Therefore, these inherent problems associated with respiring food products such as swiss-type cheeses must be addressed by utilizing film structures and packages made therefrom which will deal with these problems in an efficient manner.
The problems described above are evident in the packaging of most respiring food products and the known products typically are suitable for these uses. However, there are further problems associated with the packaging of respiring food products which generate higher levels of CO2 naturally, such as the packing of large quantities of cheese. As can be appreciated, the weight of a block of cheese can be doubled by doubling the thickness of the cheese. However, doubling the thickness of the package to accommodate the larger weight typically does not double the area of the package. Therefore, the generation of a large amount of CO2 may result in an amount of CO2 that can not be accommodated by the film structure without decreasing the effectiveness of oxygen barrier.
Therefore, there exists a need for a film structure and package that can allow CO2 to flow out of a package containing a large quantity of respiring food yet also allow in flow of a limited quantity of O2 while providing stiffness, and a moisture barrier and maximizing flex crack resistance. Also, the film structures and packages must be cost-effective.